To provide a ball endmill which can reduce a cutting resistance in cutting a rising wall surface having a tilting angle, and can lengthen the tool life, and can improve the machining accuracy.

The ball endmill having two to ten outer helical cutting edges continued from the R edge 12 of the tip end ball surface has a back taper on the outer peripheral cutting edge 2, 5 of the outer peripheral cutting edge portion 1, 4 so as to reduce the cutting resistance when the rising wall surface having the tilting angle is cut by means of the ball endmill. Preferably, the back taper angle is 0.5° to 5°.